Device for controlling the raising and lowering movement of a fluidized bed

Abstract

A device for controlling the raising and lowering of a fluidized bed for supporting a human body on a bed of particles which can be made to float and flow by supplying air under pressure thereto. A drive unit vertically raises or lowers the bed in response to a vertical movement command issued by a control unit. A flow stop command is issued for stopping the operation of an air compressor, which floats the beads, when the vertical movement command is generated. The vertical movement command is inhibited during a predetermined interval after the command has been generated in order for the flow of compressed air to stop to allow the beads to come to rest before the bed is raised or lowered.

I claim: 
     
       1. A device for controlling the raising and lowering of a fluidized bed for supporting a human body on a bed of particles floating and flowing with air under pressure, comprising: a drive unit for vertically raising and lowering the bed;   control means for issuing a vertical movement command to said drive unit;   vertical movement control means for controlling operations of said drive unit in response to the vertical movement command from said control means;   flow control means for controlling flowing movement of air in said bed;   means for issuing a flow stop command to said flow control means when said vertical movement command is generated by said control means and for issuing a flow start command to said flow control means when generation of said vertical movement command is stopped; and   means for inhibiting the vertical movement command applied from said control means to said vertical movement control means during a predetermined interval of time after the vertical movement command has been generated until said bed of particles stops its flowing movement.   
     
     
       2. The device for controlling the raising and lowering of a fluidized bed of claim 1, wherein said inhibiting means comprises a first timer having as a trigger input said vertical movement command. 
     
     
       3. The device for controlling the raising and lowering of a fluidized bed of claim 2, further comprising a second timer, said second timer being triggered at an end of said vertical movement command, an output of said second timer being applied to inhibit said means for issuing a flow stop command during a second predetermined interval of time after the end of said vertical movement command. 
     
     
       4. The device for controlling the raising and lowering of a fluidized bed of claim 3, further comprising an AND gate having an output connected to a control input of said means for issuing a flow stop command, a first input coupled to an output of said second timer, and a second input receiving said vertical movement command inverted.